Flow-Induced Delivery from a Drug Mass

ABSTRACT

Drug solutions (or other combinations of vehicle with entrained drug) are prepared by removing drug from one or more masses of a solid form of the drug. The solid form of the drug may be sparingly soluble or insoluble in water. Examples of devices for holding solid drug and facilitating delivery of such drug to targeted regions are also described.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Ser.No. 60/804,394 (attorney docket number 006501.00022), filed Jun. 9, 2006and titled “Drug Delivery by Flow Dissolution,” hereby incorporated byreference herein.

BACKGROUND

Use of drugs in combination with devices capable of tissue-specificdelivery poses special problems for drug formulation. In some cases, theformulation should be stable over an extended period of time, especiallyif that formulation is intended for use in an implanted drug deliverydevice.

SUMMARY

This Summary is provided to introduce a selection of concepts in asimplified form that are further described below in the DetailedDescription. This Summary is not intended to identify key or essentialfeatures of the claimed subject matter, nor is it intended to be used asan aid in determining the scope of the claimed subject matter.

At least some embodiments of the invention address problems posed bytissue-specific drug delivery devices. In at least some suchembodiments, a solid form of a drug is stored in the device anddelivered to a desired region using an appropriate vehicle. Embodimentsof the invention also include preparing a solution (or suspension) of atherapeutically effective concentration of a drug which is sparinglysoluble in water, with the solution (or suspension) being formed byremoval of drug from a mass of solid drug using an appropriate vehicle.

BRIEF DESCRIPTION OF THE FIGURES

The following detailed description is better understood when read inconjunction with the accompanying drawings, which are included by way ofexample, and not by way of limitation. Some of the drawings includeshading. Shading is provided only for the purpose of enhancingreadability, and the presence or absence of shading in a particulardrawing is not otherwise intended to have significance.

FIG. 1 shows a drug delivery device according to one embodiment.

FIG. 2 is a cross-sectional view of a sleeved drug chamber from FIG. 1.

FIGS. 3A through 3C are cross-sectional views of drug chambers includingscreens.

FIGS. 3D and 3E are perspective and cross-sectional views, respectively,of a drug chamber that includes an air vent.

FIG. 3F is a perspective view of a drug chamber that includes flats.

FIG. 4 shows a sleeved drug chamber joined to catheters and to a 3-Dantibacterial filter.

FIG. 5 is a cross sectional view of a solid drug and 3-D antibacterialfilter housing.

FIG. 6 shows a subcutaneously-implantable port attached with a catheterto a sleeved drug chamber.

FIG. 7 shows an open subcutaneously-implantable port containing pelletsof solid drug.

FIGS. 8 and 9 show a two piece solid drug and 3-D antibacterial filterhousing according to another embodiment.

FIG. 10 is a cross-sectional view of the sleeved drug chamber from FIG.2, with example dimensions included.

FIG. 1 shows an embodiment in which a dual lumen tube extends from apump and/or reservoir containing solid drug.

FIG. 12 is an enlarged view of the distal ends of the dual lumen tubeshown in FIG. 11.

FIG. 13 is a perspective view showing an embodiment in which asemi-permeable membrane allows interstitial fluid to pass into a chambercontaining a solid drug.

FIG. 14 is a fully cross-sectional view of the embodiment of FIG. 13.

FIG. 15 shows the embodiment of FIGS. 13 and 14 containing solid drugpellets.

FIG. 16 shows an embodiment where fluid is circulated unidirectionallythrough a loop containing a semi-permeable hollow fiber.

FIG. 17 is an enlarged view of the distal end of the embodiment of FIG.16, and shows additional details of the hollow fiber loop.

FIG. 18 is a cross-sectional view of the connection between the hollowfiber and non-permeable tubing of FIG. 17.

FIGS. 19 through 22 show an embodiment implementingelectrophoresis-stimulated delivery of drug.

FIGS. 23 and 24 show an embodiment implementing magnetically-stimulateddelivery of drug.

FIG. 25 is another embodiment implementing magnetically-stimulateddelivery of drug.

FIG. 26 shows the elution of gacyclidine from a drug dissolution chamberas a function of the concentration of hydrochloric acid in Ringer'ssolution used to erode pellets of crystalline gacyclidine base.

DETAILED DESCRIPTION

At least some embodiments include methods for delivering atherapeutically effective concentration of a drug for which either theacidic or basic form of the drug is water insoluble or sparinglywater-soluble. As used herein, a drug form is “sparingly water-soluble”if only an insignificant amount of that drug form can be dissolved bywater alone. For a drug with acid-base functional groups, a lesswater-soluble form is likely to be more stable than a form of the drugwhich is water-soluble. This is a consequence of such a form being lessprone to solution-dependent decomposition processes, especially if thedrug is stored as a solid (e.g., in a crystalline state). Moreover, acrystalline or amorphous solid drug will often occupy a smaller volumethan is required for another form of the drug. This can facilitateconstruction of small delivery devices and/or reservoirs for storing adrug. When a drug is stored in solid form, properties of a vehicle canbe used to control the rate at which drug is removed (whether bydissolution, elution, erosion or some other mechanism or combination ofmechanisms) from one or more masses of solid drug, thereby offering aflexibility for modulating a concentration of drug that is delivered toa tissue or other target region.

As used herein (including the claims), a “vehicle” is a fluid mediumused to remove solid drug from one or more masses of solid drug and/orto deliver the removed drug to a target tissue or to some other desiredlocation. A vehicle can be a bodily fluid, an artificial fluid or acombination of bodily and artificial fluids, and may also contain othermaterials in addition to a drug being removed and/or delivered. Avehicle may contain such other materials in solution (e.g., NaCl insaline, a solution of an acid or base in water, etc.) and/or suspension(e.g., nanoparticles). Further examples of vehicles are included below.

Drug that is removed from a solid drug mass by a vehicle and retained inthat vehicle is sometimes referred to herein as being entrained within(or by) the vehicle. As used herein (including the claims), “entrained”drug includes drug that is eroded from a mass and dissolved in thevehicle, drug that is eroded from a mass and suspended in the vehicle,and drug that is eroded from a mass and adsorbed/absorbed tonanoparticles or other components of the vehicle. A drug that is removedfrom a solid drug mass and remains within the vehicle in anotherchemical form (e.g., a salt that results when a basic solid drug mass isplaced into contact with an acidic vehicle) is also included within thescope of the phrase “entrained drug.”

According to at least some embodiments in which the basic form of asolid drug is less soluble than an acidic solid form, solid pellets ofthe basic form are eluted with an acid at a concentration that issubstantially the same as the desired drug concentration. In at leastsome embodiments in which the acidic form of a drug is less soluble thanthe basic form, solid pellets of the acidic form are eluted with a baseat a concentration that is substantially the same as the desired drugconcentration. According to at least some additional embodiments, anaqueous solution comprising one or more components having an amphipathicmolecule which can solubilize a water-insoluble drug can be used toerode a solid drug pellet to effect delivery of a therapeuticallyeffective amount of the drug.

At least some embodiments also include a drug reservoir which cancontain one or more masses of one or more solid drugs. The solid drugcan be eluted from the reservoir with an appropriate solution or othervehicle capable of effecting solid drug dissolution or otherwise capableof removing small amounts of drug from the one or more solid drug massesat a desired rate.

An advantage of using solid drug in an implanted device is, in at leastsome embodiments, the ability to store drug in the device using asmaller volume than might be required if a premixed (or other liquid)form of the drug were used. In some cases, this smaller volume enablesimplantation of a device containing enough drug to provide (whencombined with an appropriate vehicle source) substantially continuouslong term therapy. This long term therapy can be over a period of days,weeks, or months. In some cases, long term therapy may extend overseveral years. One example of a basic crystalline or solid amorphousdrug suitable for use in methods according to some embodiments isgacyclidine. It is estimated that 18 mg of gacyclidine will deliver 100μM drug over 4 years at a flow rate of 20 microliters per hour. Thehydrochloride salt of gacyclidine, its acidic form, is highly watersoluble. However, the acidic form of gacyclidine is also unstable atbody temperature. By contrast, the basic form of gacyclidine issparingly soluble in water and is much more stable than its acidic formin the presence of water. Dissolution of the basic form of gacyclidinein water requires the presence of an acid (e.g., hydrochloric acid orlactic acid) to convert the basic form to the water-soluble acidic form.The concentration of gacyclidine in solution will therefore depend onthe amount of acid available to convert the basic form to the acid form.This ability of an appropriate vehicle to change the amount of drugdissolved and delivered offers substantial flexibility in changing theconcentration of delivered drug, without requiring the changing of adevice holding the solid drug, and without loading a differentconcentration of a therapeutic solution into a liquid reservoir.

One example of an acidic crystalline drug that is suitable for use inmethods according to some other embodiments is carbamathione. See U.S.Patent Application Publication No. 2005/0130904. Carbamathione containsfour acid-base functionalities: two carboxylic acids, one thiol group,and one amino group. In its monobasic-triacidic form, carbamathione willreadily form crystals that are sparingly soluble in water. Dissolutionof this form of the drug in water requires one equivalent of base, suchas sodium bicarbonate or sodium hydroxide, to convert this form to thedibasic-diacidic form, which is water soluble.

Methods of the invention are not limited to delivery of gacyclidine orcarbamathione. At least some embodiments include methods applicable todelivery of any drug which is water (or other vehicle) soluble in one ofan acid or base form and sparingly soluble in the other of the acid orbase form. A solid comprised of the less water soluble drug form iseluted or eroded with a compatible vehicle (e.g., Ringer's solution,Ringer's lactate, saline, physiological saline, artificial perilymph)comprising, as appropriate, either an acid or a base. If the lesswater-soluble drug form is a basic form, then the vehicle can contain apharmaceutically acceptable acid, such as hydrochloric acid, monobasicsodium phosphate (e.g., monosodium phosphate), lactic acid, phosphoricacid, citric acid, a sodium salt of citric acid, or lactic acid. If theless water-soluble drug form is an acidic form, then the vehicle cancontain a pharmaceutically acceptable base, such as sodium hydroxide,sodium bicarbonate, or choline hydroxide.

Methods according to at least some embodiments of the invention canemploy solid drug pellets. Those pellets can be crystalline masses orsolid amorphous masses. One example of manufacturing drug pellets isincluded herein as Example 1. A solid drug could also include acombination of crystalline and amorphous masses. The drug can be meltmolded into any desired shape or can be pressed into pellets usingpressure. Crystalline drug (if available) may be more desirable thanamorphous solid drug forms in some cases, as crystalline substancestypically are more stable. Crystal lattice energy may also helpstabilize the drug. However, the invention is not limited to crystallinedrug forms or the use thereof.

The invention is not limited to drugs (or to methods or devicesemploying drugs) with acid-base functionalities. Embodiments alsoinclude dissolution (or removal from a mass by other mechanism) of anydrug which is sparingly soluble in water by eluting the drug with apharmaceutically acceptable vehicle (e.g., saline, Ringer's lactate,artificial perilymph, Ringer's solution) comprising one or morecomponents having an amphipathic molecule, such as monopalmitoylglycerol or polysorbate 80 (e.g., TWEEN 80®). Other suitable amphipathicmolecule components include (but are not limited to) an acyl glycerol, apoly-oxyethylene ester of 12-hydroxysteric acid (e.g., SOLUTOL™ HS15),beta-cyclodextrin (e.g., CAPTISOL®), a bile acid such as taurocholicacid, tauroursodeoxycholic acid, cholic acid or ursodeoxycholic acid, anaturally occurring anionic surfactant such as galactocerebrosidesulfate, a naturally occurring neutral surfactant such aslactosylceramide or a naturally occurring zwitterionic surfactant suchas sphingomyelin, phosphatidyl choline or palmitoyl carnitine.Dissolution (or other removal) can also be accomplished by use ofphysiological fluid vehicles, such as cochlear perilymph, cerebrospinalfluid, or interstitial fluid. Physiological fluid vehicles containamphipathic molecules, such as proteins and lipids, which are capable ofeffecting dissolution of a water-insoluble drug. Dissolution can also becarried out without the use of an amphipathic molecule where anacceptable concentration of drug is obtained.

One example of a drug that does not have acid-base functionalities istriamcinolone acetonide. Triamcinolone acetonide is commerciallyavailable as a crystalline solid with very low water solubility. Ifsolid pellets of triamcinolone acetonide are exposed to a continuousstream of a vehicle, such as Ringer's solution, the expectedconcentration of extracted triamcinolone acetonide in solution should be40 μM or less. A higher concentration of triamcinolone acetonide can besolubilized by including an amphipathic molecule in the vehicle. Such apharmaceutically acceptable amphipathic molecule would be polysorbate80. The concentration of triamcinolone acetonide solubilized can beincreased above its water solubility, 40 μM, by adding the requiredamount of amphipathic molecule to the vehicle that will support thedesired drug concentration. The invention is not limited to methodsimplemented through use of triamcinolone acetonide, Ringer's solution orpolysorbate 80. Any sparingly soluble drug, pharmaceutically acceptablevehicle and pharmaceutically acceptable amphipathic molecule can beused.

Nanoparticles can maintain a drug in a mobile phase capable of passingthrough an antibacterial filter. Some embodiments would use, in place ofor in combination with an amphipathic drug carrier, a suspension ofparticles (e.g, nanoparticles) that would have affinity for a drug(e.g., that would adsorb/absorb a drug) and act as carriers. Still otherembodiments include use of pure drug nanoparticles. Yet otherembodiments include combinations of both pure drug nanoparticles anddrug adsorbed/adsorbed to carrier nanoparticles. Particles according toat least some embodiments would be small enough to pass through anantibacterial filter of 0.22 microns or less. Removal of a drug from amass thereof using a vehicle having suspended carrier nanoparticleswould be advantageous to both drug stability and delivery. Removal ofsolid drug from a mass of drug nanoparticles would have similarbenefits.

As indicated above, in at least some embodiments a vehicle includes asuspension of small carrier particles (100 nm to 0.1 mm in size) orcarrier nanoparticles (10 nm to 100 nm in size) having an affinity forthe drug(s) to be delivered. Examples of materials from which thecarrier particles or nanoparticles could be formed include (but are notlimited to) polylactic acid, polyglycolic acid, a co-polymer of lacticacid and glycolic acid, polypropylene, polyethylene and polystyrene.Additional examples of materials from which carrier particles ornanoparticles can be formed include magnetic metals and magnetic metalshaving a coating to attract a drug (or drugs) of interest. These smallcarrier particles or nanoparticles will adsorb/absorb or otherwiseattract drug that is eroded from a mass of solid drug (which may bestored in a reservoir such as is described herein) by a vehicle in whichthe carrier particles (or nanoparticles) are suspended.

In some embodiments, a vehicle will be to used to erode pure drugnanoparticles from a solid mass composed of such pure drugnanoparticles. Such a solid mass of nanoparticles could be formed bycompression and/or by use of a binder.

In some cases, a small amount of acid or amphipathic excipient (e.g.,SOLUTOL® HS15, TWEEN 80® or CAPTISOL®) can be employed to facilitatedrug removal from a mass of solid drug (or from a mass of solid drugnanoparticles) and transfer to a mobile nanoparticle suspension.

In some embodiments, polymeric material used to fabricate carriernanoparticles is biodegradable (so as to help promote ultimate deliveryof drug), commercially available and approved for human use. Polymers ofL- and D,L-lactic acid and copolymers of lactic acid and glycolic acid[poly(lactide-co-glycolide)] (available from Lakeshore Biomaterials inBirmingham, Ala.) are examples of polymeric materials that have thepotential to meet the desired properties of the polymer for carriernanoparticles. Nanoparticles small enough to pass through a 0.22 μmantibacterial filter have been fabricated from a 50:50 mix ofpoly(lactide-co-glycolide) by the solvent replacement method.

Several methods have been employed to fabricate nanoparticles ofsuitable size. These methods include vaporization methods (e.g., freejet expansion, laser vaporization, spark erosion, electro explosion andchemical vapor deposition), physical methods involving mechanicalattrition (e.g., pearlmilling), interfacial deposition following solventdisplacement and supercritical CO₂. Additional methods for preparingnanoparticles include solvent displacement of a solubilizing solvent anda solvent in which the nanoparticle is not soluble, vibrationalatomization and drying in the atomized state, sonication of two liquidstreams, use of micropumps (such as ink jet-like systems delivering nanoand micro-sized droplets of drug) and continuous flow mixers.

When preparing nanoparticles by the solvent displacement method, astirring rate of 500 rpm or greater is normally employed. Slower solventexchange rates during mixing produce larger particles. Fluctuatingpressure gradients are fundamental to producing efficient mixing infully developed turbulence. Sonication is one method that can provideadequate turbulent mixing. Continuous flow mixers (two or more solventstreams) with and without sonication may provide the necessaryturbulence to ensure small particle size if the scale is small enough.The solvent displacement method has the advantage of being relativelysimple to implement on a laboratory or industrial scale and has producednanoparticles able to pass through a 0.22 μm filter. The size ofnanoparticles produced by the solvent displacement method is sensitiveto the concentration of polymer in the organic solvent, to the rate ofmixing and to the surfactant employed in the process.

Pure drug nanoparticles can be prepared by neutralization of a dissolvedacid or basic drug or dilution of the dissolved drug (in insoluble form)with a miscible solvent in which the drug is not soluble. With rapidmixing and the introduction of the precipitating solvent at the correctspeed for that particular drug, nanoparticles are produced.Alternatively, drug nanoparticles can be derived from atomizedmicroparticles that were dried while suspended in a drying gas andcollected. Solid nanoparticle masses suspended in a solvent (forexample, composed of pure basic gacyclidine) can be isolated byaccelerated sedimentation rates with a centrifuge (e.g., a Hermle Z229centrifuge operating at 15,000 rpm with an average g force of 30,000 g(25,000 g to 35,000 g)) either with a binding agent to facilitate thepellet formation or by mixing later with the binding agent and/or bycompression of a dried pellet. There is a correlation between particlesize and sedimentation rate according to Stoke's Law[v=D²(ρ_(p)−ρ₁)g/18ρ]. At one gravity, the time required forsedimentation of a 100 nm particle will be about 200 days, while a 10 nmparticle will take approximately six years to settle out. The exact timerequired for sedimentation will depend on particle density (ρ_(p)),liquid density (ρ₁), liquid viscosity (η) and particle diameter (D).Once isolated the dried or wet pellet of drug particles can becompressed into a solid mass or mixed with a pharmaceutically acceptablebinder and compressed into a mass.

In at least some embodiments, a device employed for removal of drug froma solid drug mass with (and entrainment by) a vehicle can include anychamber capable of holding a less water-soluble form of the drug andpermitting a vehicle comprising a dissolving or other removal agent(e.g., acid, base, an amphipathic molecule, a suspension ofnanoparticles) to flow past the solid drug. The size of the chamber,rate of vehicle flow and concentration of acid, base, amphipathicmolecule or nanoparticles used are determined by the intendedapplication of the drug delivery device and dissolution characteristics(or erosion or other physical characteristics) of the drug substanceand/or drug mass, as well as by any required vehicle reservoir and/orpumping system. Determination of the parameters for such a device iswithin the ability of one skilled in the art, once such a person isprovided with the information included herein.

Fluid flow to effect drug dissolution (or removal by other mechanism)can be accomplished by any pump with fluid flow parameters that matchthe desired application. Such pumps include, but are not limited to,syringe pumps (e.g., the MiniMed 508 pump described below in Example 2),a MEMS pump, an osmotic pump, a peristaltic pump, a piston pump,piezo-electric pump and the like. Selection of an appropriate pump issimilarly within the ability of one skilled in the art, once such aperson is provided with the information included herein. In someembodiments, a pump can be fully implanted within a human (or otheranimal) body. In other embodiments, a pump may be external to the bodyand delivering vehicle through a subcutaneous port or other connectionto a reservoir holding solid drug.

In at least some embodiments, solid drug can be removed from a massthereof using a liquid that is delivered from an implanted or externalsource containing a fluid such as saline, Ringer's solution, Ringer'slactate, or artificial perilymph in order to dissolve or otherwise loadthe drug into the liquid. The drug-laden liquid solution is thendelivered to the target tissue. Examples of target tissues include, butare not limited to, a cochlea, lymph nodes, tumors, a brain, a spine,etc.

In at least some embodiments, a fully implantable drug delivery deviceincludes a fluid delivery device, such as an osmotic pump, in fluidcommunication with a drug-containing chamber and a three-dimensionalantibacterial filter. One embodiment is shown in FIG. 1. In theembodiment of FIG. 1, device 10 includes an osmotic pump 12 coupled to asleeved drug reservoir 14 via a catheter 16 and 17. A three-dimensional(3-D) antibacterial filter 19 is coupled to drug reservoir 14 via acatheter 18. Another catheter 21 and connector 22 connects 3-D filter 19via an additional catheter (not shown) to a terminal component (also notshown) positioned for delivery of a drug-laden solution into the targettissue. The terminal component may be, e.g., a needle, a cochlearimplant electrode, a cochlear catheter, or even an open end of acatheter. Drawing FIG. 1 from U.S. patent application Ser. No.11/414,543 (filed May 1, 2006 and titled “Apparatus and Method forDelivery of Therapeutic and other Types of Agents”) illustrates anembodiment where the terminal component is a bone needle. Prior toimplantation, the osmotic pump is filled with a solution that willdissolve the solid drug.

A solid drug reservoir is designed to provide a cavity for fluid to flowaround and erode one or more masses of solid drug (e.g., solid drugpellets). FIG. 2 is a cross-sectional view of sleeved drug reservoir 14of FIG. 1, which is but one example of a drug reservoir according to atleast some embodiments. Drug reservoir 14 includes two hollow metaltubes 28 and 29 (made from a drug compatible material) forming a chamber20 into which multiple solid drug pellets 25 are loaded. A sleeve 27(made from silicone or other appropriate material) is rolled over tubes28 and 29 to form a liquid tight seal. Tapered ends of tubes 28 and 29fit into ends of catheters 18 and 17, respectively. Drug reservoir 14 ofFIG. 2 is shaped to contain the drug pellets within chamber 20 andprevent solid pieces from moving out of chamber 20. Drug reservoir 14may also be pulled apart and reattached to thereby allow loading of oneor more solid drug pellets.

In some embodiments, circular screens are placed inside a drug chamberto further prevent migration of drug pellets. In some cases, at leastone of the screens may be removable to allow for replenishment of drug.FIGS. 3A and 3B are cross-sectional views of a drug reservoir 40according to another embodiment, and that includes such screens. As seenin FIGS. 3A and 3B, drug reservoir 40 includes housings 44 and 46 thatmate together (with threads 51 and 52) to form a fluid-tight connection.Solid drug can be placed inside chamber 42 within housing 44, withhousing 44 including a stationary meshed screen 43 on the side of tubingconnection inlet 50 and a removable meshed screen 41 at the edge ofhousing 44. As seen in FIG. 3A, screen 41 is directly before 3-Dantibacterial filter 45, which rests within housing 46. Screens 41 and43 are porous and may be woven wire cloth made of titanium, stainlesssteel, or biocompatible, drug compatible polymers such asfluoropolymers. In other embodiments, the screens may be made of porousmetal, such as titanium or stainless steel. Meshed screens 41 and 43prevent drug pellets from going into the housing 46, antibacterialfilter 45 or tubing (not shown) that may be connected to inletconnection 50 or outlet connection 48. In FIG. 3A drug reservoir 40 isshown with housing halves 44 and 46 threaded together. FIG. 3B showshousings 44 and 46 separated, but with removable screen 41, stationaryscreen 43 and antibacterial filter 45 in place. As seen in FIG. 3B,removable screen 41 covers the outer circular surface of the end ofhousing 44. Stationary screen 43 only covers the inner circular surfaceof space 42. Screens can be of any shape to fit the shape of the drugchamber. Screens are not required, however, and may be omitted incertain embodiments.

An antibacterial filter is similarly not required. For example, FIG. 3Cis a cross-sectional view of drug reservoir 40 without antibacterialfilter 45. At least some embodiments may also include features whichpermit air bubbles to bleed off during filling of the system. This canhelp to prevent vapor lock in cases where a fluid delivery system (e.g.,an osmotic pump or an external pump) does not generate sufficientpressure to overcome surface tension holding liquid withincapillary-like structures of a wet porous filter (such as 3-D filter 45of FIGS. 3A and 3B). In some embodiments, a set screw or plug may beincorporated into the side of a drug chamber housing on the upstream(i.e., higher pressure) side of the filter. The set screw or plug may beremoved during priming and reattached for use once all air bubbles havebeen bled from the system. In still other embodiments, a vent valve mayinclude an upstream semi-permeable membrane allowing for venting ofgases. In yet other embodiments, the set screw or plug may benon-removable, but may include a portion which is gas-permeable but notliquid-permeable so as to allow degassing.

FIG. 3D shows a drug reservoir 60 according to at least one embodiment,and which includes vent valve 61 having a semi-permeable membraneallowing for venting of gases. Tubing connector barb 62 is on theupstream side of reservoir 60, and tubing connector 63 is on thedownstream side. FIG. 3E is a cross sectional view of drug reservoir 60.Drug reservoir 60 includes housings 64 and 65 which join to form afluid-tight connection with threads 71, 72. A cavity 66 holds one ormore solid drug pellets or other masses. Although not shown, screenssimilar to screens 43 and 41 in FIGS. 3A and 3B can be placed (in eithera stationary or removable configuration) over face 69 on the upstreamside of space 66 and over face 68 on the downstream side of space 66. Inthe embodiment of FIG. 3D, a 3-D antibacterial filter 67 fits within aspace 74 formed in housing 65.

Housings 44 and 46 of drug reservoir 40, housings 64 and 65 of drugreservoir 60, and housings of drug reservoirs in other embodiments canbe made of a drug-compatible, corrosion-resistant material such astitanium, stainless steel, a biocompatible coated metal, a chemicallyinert polymer such as PTFE, FEP, PFA and other fluoropolymers or afluoropolymer-coated metal. During low flow rates at body temperature,drug may tend to adsorb to the walls of the chamber, causing lower thanexpected concentrations of drug to be delivered to the patient.Fluoropolymers are the best known materials for resisting adsorption.

As indicated above, drug reservoirs in various embodiments may be openedand closed to allow for replenishment of solid drug. The reservoircomponents may be threaded (as shown in FIGS. 3A-3C and 3E) or mayconsist of a locking tab and groove. In still other embodiments anexternal clamp may be used. In yet other embodiments, reservoir housingsmay be joined by a snap-fit. As also indicated above, reservoir 14 (FIG.2) includes two metal tubes 28 and 29 held together by a surroundingsleeve 27. Surrounding sleeve 27 may be made of a flexible polymer suchas silicone rubber. In some embodiments, a biocompatible gasket can beplaced between mating portions of a drug reservoir (e.g., between tubes28 and 29 of FIG. 2, between housings 44 and 46 of FIGS. 3A-3C, betweenhousings 64 and 65 of FIG. 3E) to prevent leaks. In still otherembodiments, external portions of a drug reservoir housing may includeflats or other regions to facilitate easier tightening. FIG. 3F shows anembodiment of a drug reservoir 80 having mating housings 81 and 82. Aflat 83 is formed on one side of housing 81. A second flat (not shown)can be formed on an opposite side of housing 81. Similarly, housing 82includes a flat 84 formed on one side, and can also include anadditional flat (also not shown) on an opposite side.

In at least some embodiments, catheter tubing on the upstream side of adrug reservoir (e.g., tubing for catheter 16 on the pump side of device10 in FIG. 1) is a vehicle- and biocompatible, flexible polymer such assilicone, polyurethane, or fluoropolymer including PTFE, FEP, and PFAand the catheter tubing on the downstream side of the drug reservoir isa biocompatible, drug compatible, flexible polymer such as PTFE, FEP andother fluoropolymers.

In some embodiments, the solid drug reservoir and a 3-D antibacterialfilter are in fluid communication via catheter connection. This is seengenerally in FIG. 1, and in more detail in FIG. 4 (where upstream anddownstream directions are indicated). Also shown in FIG. 4 are metaltubing connectors 22 and 89 that can be used to connect to upstream ordownstream components. In another embodiment, a single housing maycontain solid drug as well as a three-dimensional antibacterial filter.One example of such a configuration can be seen in drawing FIG. 2 fromcommonly-owned U.S. patent application Ser. No. 11/414,543 (titled“Apparatus and Method for Delivery of Therapeutic and Other Types ofAgents” and filed May 1, 2006), the housing for which holds a separatecontainer (a cage in that case) for drug. Such a housing may also beopened and closed to allow for replenishment of solid drug. FIG. 5 is across-sectional view of a drug reservoir 95 according to anotherembodiment. Drug reservoir 95 includes housings 96 and 97 joined bymating threads 101, 102. A cavity 103 inside housing 96 holds solid drug(not shown). Screens similar to screens 41 and 43 of FIGS. 3A and 3B mayalso be included. A 3-D antibacterial filter 98 is located in a space99. Instead of the barbed fittings shown in FIGS. 3A-3F, drug reservoir95 includes an upstream inlet hole 105 and a downstream inlet hole 106.

In some embodiments the solid drug reservoir is asubcutaneously-implantable port (or is in fluid communication with sucha port). One such embodiment is shown in FIG. 6, where osmotic pump 12of device 10 (FIG. 1) has been replaced with a subcutaneous port 110. Inother embodiments, a subcutaneously-implantable port reservoir containssolid drug pellets which are eroded by a vehicle that is introduced intothe port via a needle that pierces a septum of the port (with the needlein fluid communication with an external pump or some other source ofvehicle). FIG. 7 shows a subcutaneously-implantable port 120 with itscover (and septum) removed, and containing solid drug pellets 25. Asalso shown in FIG. 7, a 3-D antibacterial filter 121 may be attached toan outlet of port 120.

A 3-D antibacterial filter could alternatively be located elsewherebetween the drug-holding cavity of port 120 and the distal end of acatheter delivering drug from port 120. The shape of the solid drug canbe molded into any appropriate shape.

In at least some embodiments, a housing for a drug and filter is madefrom titanium and is small enough to be implanted into a human body. Theinner diameter is sized so that a 3-D antibacterial filter can be bondedto the inside of the housing. Examples of possible filter sizes (invarious embodiments) include but are not limited to 0.2 micron pore size3-D filters with a physical outer diameter of 0.03 to 0.25″. In stillother embodiments the physical outer diameter is between 0.1″ and 0.3″.

FIG. 8 is a perspective view of two separated housings 126 and 127 adrug reservoir 125 according to at least one embodiment. FIG. 9 is across-sectional view of drug reservoir 125, with housings 126 and 127joined (via threads 130 and 131). The entire outer ends of housings 126and 127 have barbs 128 and 129 (respectively) formed thereon. Also seenin FIG. 9 are a space 132 for holding solid drug and an optional 3-Dantibacterial filter 133.

FIG. 10 is a cross-sectional view of sleeved drug reservoir 14 fromFIGS. 1 and 2, and with example dimensions included. In the example ofFIGS. 1, 2 and 10, the interior chamber 20 volume is approximately 43mm³ (43 μL), with approximately 32 mm³ available to hold solid drug.

FIG. 11 shows an additional embodiment in which a dual lumen tube 145extends from a pump and/or reservoir containing solid drug. Dual-lumentube 145 separates into two separate lines. Tube 146 is attached to onelumen and receives inflowing physiological fluid from a patient. Tube147 is attached to another lumen and delivers therapeutic fluid to thepatient. Physiological fluid received in line 146 flows past solid drugpellets in the reservoir and slowly removes (e.g., by dissolution) drugfrom those pellets. The resulting solution of drug and physiologicalfluid is then delivered to a target tissue through tube 147. FIG. 12 isan enlarged view of the distal ends 148 and 149 of tubes 146 and 147,and further illustrates the two lumens for recirculating fluid flow. Inother embodiments, two completely separate tubes (i.e., two tubes thatdo not emerge from a dual lumen tube) may be used. Such an embodimentcould be useful in cases where physiological fluid is withdrawn from aregion that is more distant from the region in which therapeutic fluidis to be delivered.

FIG. 13 is a perspective view showing an embodiment of a system whichdoes not require a pump to generate flow. A semi-permeable membrane 155allows an interstitial fluid vehicle to pass into a chamber of areservoir 156 containing solid drug. As drug within the chamberdissolves (or is otherwise removed from the solid drug mass andentrained in the interstitial fluid vehicle), the concentrationdifference across the membrane causes fluid to flow from lowconcentration to higher concentration. Osmotic pressure forces fluidpast membrane 155, into the drug chamber, through the outlet, and pastan optional 3-D antibacterial filter 157 in a catheter 158 (shown as aclear catheter for purposes of illustration) to the target deliverysite. Semi-permeable membrane 155 has a pore size cutoff sufficient tolet interstitial fluid through but not let the entrained solid drugdiffuse out. Antibacterial filter 157 has pores sufficient to retainbacteria but to let dissolved (or otherwise entrained) drug passthrough. An electric field may also be applied to membrane 155 resultingin diffusion by electro-osmosis. FIG. 14 is a fully cross-sectional viewof the embodiment of FIG. 13, and shows in more detail a cavity 160 forholding a solid drug. FIG. 15 shows the embodiment of FIGS. 13 and 14containing solid drug pellets 25 in cavity 160. Appropriate check valves(not shown) can be included within cavity 160 or elsewhere in the fluidpath so as to prevent backflow.

FIG. 16 shows an embodiment of a system 170 where fluid is circulatedunidirectionally from a pump/reservoir (via one lumen of dual-lumentubing 175) through a loop 172 containing a semi-permeable hollow fiber173 and returned through a second lumen of tubing 175. Hollow fiber loop173 is a terminal component which can be positioned at a target deliveryarea. The pump circulates vehicle past solid drug located in thereservoir, and the resulting drug-loaded vehicle diffuses through thewalls of hollow fiber 173 into the target tissue. FIG. 17 is an enlargedview of hollow fiber loop 172 shown in FIG. 16, with the variouscomponents made partially transparent for purposes of explanation. Loop172 containing hollow fiber 173 is attached to respective inflow andoutflow lumens in dual-lumen tube 175 with non-permeable tubing sections176 and 177. FIG. 18 is a cross-sectional view of the connection betweenhollow fiber 173 and non-permeable tubing sections 176 and 177.Connectors 178 may be made of titanium, stainless steel, or otherbiocompatible, drug compatible metals or polymers.

Still other embodiments include pH and/or round window noise sensors(e.g., an ultra micro microphone) with attached battery and powerelectronics (power supply, recharging circuitry, etc.) and communicationelectronics to receive and send information. In these embodiments, theelectronics could be bundled with the reservoir section of the deviceand the sensors could be combined with a wire following the surface ofthe catheter or contained within one of the lumens of a multi-lumentubing and exiting within a cochlea or other target tissue.

At least some embodiments include electrophoresis-stimulated delivery ofcharged drug ions or other particles of drug. For charged drugs,applying an electric field on a fluid containing the drug (or containingnanoparticles that have adsorbed/absorbed drug) can induce the migrationof the drug faster than normal diffusion. In the case of gacyclidine, anegative charge on a device exit (e.g., at the end of a catheter) orjust outside of a device exit can be used to accelerate the drugdelivery to the cochlea or any other target tissue without the need fora pump. A same or similar charge of opposite polarity (e.g., a positivecharge in the case of gacyclidine) could similarly be applied to a drugcontaining compartment (e.g., a chamber in which solid drug is held),thereby enabling drug delivery out of the device without the need for apump. The electrophoresis environment would induce an electro-osmoticflow to the natural low resistance outlet within the cochlea or targettissue. The rate of migration of drug to the catheter tip (or theconcentration of drug) could be modulated by field strength of theelectric charge and other parameters modulated by an appropriateelectronics package, battery, recharging assembly, on/off switch,communication circuitry and other electronics. If a drug having anopposite charge is used, then the electronic circuitry would reverse thecharges on the electrodes. Electrophoresis-stimulated drug deliveryembodiments would be very low power devices in order to promote patientsafety, and because small amounts of drug are being delivered. A chargeddevice in a cochlea may provide additional benefits to tinnitus patientswho report benefit from electrical stimulation. Indeed, in someembodiments a catheter includes an electrode that is only used fordelivery of electrical stimulation (pulsed or otherwise) to a cochlea.In still other embodiments, a catheter includes an electrode that isalternatively (or additionally) used to sense noise, electricalpotential or some other physical characteristic in a cochlea or in someother target tissue. Methods and electronics for such stimulation and/orsensing are known in the art (although not in combination with the drugdelivery devices described herein). Because inclusion of appropriatestimulation and/or sensing electronics into the herein-described drugdelivery systems would be within the routine skill of a person ofordinary skill in the art once such a person is provided with theinformation contained herein, additional details of such stimulationand/or sensing electronics is not included.

FIG. 19 shows an electrophoresis-stimulated drug delivery system 195according to at least some embodiments. Tube 197 contains a fluiddelivery lumen and an electrode wire, and extends from drug reservoir196. FIG. 20 is a cross-sectional view of drug reservoir 196 and aportion of tube 197. Reservoir 196 includes a semi-permeable membrane200 and an internal cavity 201 for holding solid drug pellets. Anelectronics package 203 and battery 205 are attached to the underside ofreservoir 196. Electronics package 203 induces a charge of one polarityin electrode tip 207 and a charge of opposite polarity in a tip 208 (seeFIGS. 19 and 22) of electrode wire 209. The portion of wire 209 withincavity 201 may be coated with a dielectric or otherwise insulated toprevent premature charge exchange with tip 207. FIG. 21 is similar toFIG. 20, but shows solid drug pellets 25 within cavity 201. FIG. 22shows (in an orientation that is inverted relative to FIG. 21) theterminal (or distal) end of tubing 197 and illustrates electrode tip 208and fluid outlet 210. When opposite charges are applied to electrode 207and wire tip 208, an electro-osmotic flow is induced to a natural lowresistance outlet within a cochlea or other target tissue. Interstitialfluid enters cavity 201 through semi-permeable membrane 200. In otherembodiments, a separate tube is used (instead of membrane 200) towithdraw fluid from another bodily region that is remote from the drugreservoir. Fluid entering cavity 201 dissolves drug in cavity 201 anddelivers the drug to the target tissue.

Some embodiments include magnetic field induced delivery of drug. Twosuch embodiments are shown in FIGS. 23-25. Current applied through acoil surrounding a delivery catheter will produce a directional magneticfield. If there are magnetic or charged particles inside the catheter,they can be used to carry drug. For example, carrier nanoparticlesformed from a magnetic material can be propelled by the magnetic fieldand circulated around a loop or expelled from another type of terminalcomponent. In some embodiments (e.g., that of FIGS. 23 and 24), a hollowfiber wall allows dissolved drug to pass through but does not allowmagnetic carrier particles to pass through. Thus, the magnetic carrierwill load at the solid drug surface and release its load at the exitpore, such as the hollow fiber. The magnetic field will ensure there isa circular flow within the tubing.

FIG. 23 shows a system 210 configured to provide magnetic field induceddrug delivery. A magnetic field actuator attached to a reservoir 213induces a magnetic field so as to carry fluid and drug through a duallumen catheter 212 to a hollow fiber loop 211. FIG. 24 is an enlargedview of a portion of system 210 and shows reservoir 213 with attachedelectronics package 221, battery 215 and magnetic coil 219. Magneticcoil 219 surrounds a tube (exiting reservoir 213) containing fluid,drug, and magnetic or charged particles, and creates a magnetic fieldthat circulates the fluid around the system.

FIG. 25 shows a system 250 according to another embodiment providingmagnetic field induced drug delivery. System 250 includes a system suchas shown in FIG. 13, e.g., a reservoir 156 having a semi-permeablemembrane 156 on one end and a catheter 158 for delivery of drug to atarget region. In system 250, however, a coil 251 surrounds reservoir156 and at least a portion of catheter 158. Electronics 253 provideelectric current to coil 251 via wires 252, thereby creating a magneticfield to induce flow of charge drug particles (e.g., drug ions) from adrug chamber inside reservoir 156 and through catheter 158 to the targetregion. In some embodiments, semi-permeable membrane 155 is replacedwith a one-way valve to admit fluid (e.g., physiological fluid from abodily region in which reservoir 156 has been implanted) into the drugchamber. In some additional embodiments, electronics 253 are containedwithin the housing of reservoir 156. A 3-D antibacterial filter may alsobe included within catheter 158 or elsewhere in the system.

Embodiments of the invention can also be implemented using devices andmethods described in U.S. patent application Ser. No. 11/337,815 (filedJan. 24, 2006 and titled “Apparatus and Method for DeliveringTherapeutic and/or Other Agents to the Inner Ear and to Other Tissues,”published as U.S. Patent Application Publication No. 2006/0264897).

In some embodiments, an electronics package coupled to a drug reservoir(e.g., electronics package 203 in FIG. 20 or electronics package 221 inFIG. 24) includes components for sensing properties of a drug/vehiclesolution (or suspension). The sensed properties could include one ormore of pH, absorbance of light, electrical conductivity, lightscattering, drug or electrolyte concentrations, etc. These sensedproperties can then be used, via appropriate electronics, to adjustoperation of a pump (internal or external) or other elements (e.g.,magnetic coil or electrophoretic electrodes). An electronics packagecould also (or alternatively) be configured to detect sound or otherphysical parameters (e.g., tissue electrical activity) and/or be incommunication with remote sensors.

In at least some additional embodiments, a vehicle used to remove drugfrom one or more solid drug masses in a reservoir may itself be apre-mixed suspension of nanoparticles containing a drug (or drugs). Instill other embodiments, drug devices according to various embodimentscan be used to deliver a pre-mixed suspension of nanoparticlescontaining a drug (or drugs) without employing a solid drug mass in areservoir chamber. In either case, the nanoparticles can be drugnanoparticles or nanoparticles of a carrier material to which drug hasbeen absorbed/adsorbed or otherwise attached.

As previously indicated, devices and methods such as are describedherein can be used to provide sustained, long term delivery of a drug.Such devices and methods can also be used to provide intermittent drugdelivery on a long term basis. For example, a reservoir holding a soliddrug mass could be implanted in a patient's body. That reservoir canthen be periodically connected (e.g., using a subcutaneous port in fluidcommunication with the reservoir) to a source of vehicle.

Similar to system 10 shown in FIG. 1, the reservoirs shown in FIGS.3A-3F, 5, 8 and 9 can be implanted in a human or other animal andcoupled on one end (e.g., inlet 50 of reservoir 40, inlet barb 62 ofreservoir 60) with a catheter to a vehicle source (e.g., an implantedosmotic pump, a port into which vehicle is introduced from an externalsource). The other end (e.g., outlet 48 of reservoir 40, barb 63 ofreservoir 60) can be connected via another catheter to a terminalcomponent (which may also be implanted in the patient).

All patents, patent applications, and references cited in thisdisclosure are expressly incorporated herein by reference. The followingspecific examples are provided for purposes of illustration only and arenot intended to limit the scope of the invention.

EXAMPLE 1 Fabrication of Pellets of Gacyclidine Base

Water (500 mL) was brought to a boil. This hot water bath was then usedto melt solid gacyclidine base. After placing 35 mg of gacyclidine basein a small glass vial, the vial was incubated in the hot water bath(90-100° C.) until the gacyclidine base melted. Small aliquots (2 μL) ofthe melted gacyclidine base were then transferred to polypropylene tubes(1.5 mL in size) and allowed to stand at room temperature until thegacyclidine base had solidified.

Solidification of the melted gacyclidine is typically complete within 30minutes, but can occasionally take many hours. About half of the time, asingle solid mass is obtained that slowly grows from a single focus. Forthose aliquots that result in multiple smaller crystalline/amorphousmasses on standing, the tube containing the aliquot can be incubated ina hot water bath (90-100° C.) until it is melted a second time. Uponcooling, a second crop of single solid masses will be obtained. Thisprocess can be repeated, as necessary, until all aliquots of gacyclidinebase have been converted to single solid masses.

Single solid masses (drug pellets) obtained in this way have an averageweight of 1.5±0.3 mg and are hemispheres with a diameter of about 1.9mm. These drug pellets have sufficient mechanical stability to bedetached from the surface on which they are grown and transferred to adissolution chamber. The shape of the solid pellet is determined by theshape of the container in which the liquid drug is solidified. By usingcontainers having different shapes, drug can be solidified so as toconform to a shape of a drug reservoir in which the solid drug will beplaced.

EXAMPLE 2 Dissolution of Gacyclidine Base in a Continuous Flow Reactor

A drug chamber similar to the one illustrated in FIGS. 2 and 4 wasloaded with 11 pellets of gacyclidine base having a combined mass of 18mg. This drug-loaded chamber was eluted at a flow rate of 20 μL/hr atroom temperature (23±2° C.) using a MiniMed 508 syringe pump (availablefrom Medtronics MiniMed of Northridge, Calif.). The syringe was loadedwith 3 mL of Ringer's solution containing 0.05 to 3 mM hydrochloricacid. The eluted volume was collected in PTFE tubing attached to thepump drug capsule assembly, after a 3-D antibacterial filter. The pH ofthis solution was determined by use of a pH meter equipped with aCalomel electrode. Drug concentration was determined by HPLC.

The highest pH of the eluted drug solution (5.9) was obtained at 0.05 mMhydrochloric acid, and the lowest pH of the eluted drug solution (5.6)was obtained at 3 mM hydrochloric acid. These pH values indicatequantitative conversion of the hydrochloric acid to the drug salt andare consistent with the pH expected for solutions of the hydrochloridesalt. As shown in FIG. 26, the concentration of gacyclidine obtained inthe output from the continuous flow reactor was linearly correlated withthe concentration of hydrochloric acid used to elute the chamber. Thesedata had a correlation of 0.976±0.049 in gacyclidine concentration perhydrochloric acid concentration used for elution and an intercept atzero concentration of hydrochloric acid of 0.0014±0.0061 mM gacyclidine.

Numerous characteristics, advantages and embodiments of the inventionhave been described in detail in the foregoing description withreference to the accompanying drawings. However, the above descriptionand drawings are illustrative only. The invention is not limited to theillustrated embodiments, and all embodiments of the invention need notnecessarily achieve all of the advantages or purposes, or possess allcharacteristics, identified herein. Various changes and modificationsmay be effected by one skilled in the art without departing from thescope or spirit of the invention. Although example materials anddimensions have been provided, the invention is not limited to suchmaterials or dimensions unless specifically required by the language ofa claim. The elements and uses of the above-described embodiments can berearranged and combined in manners other than specifically describedabove, with any and all permutations within the scope of the invention.As used herein (including the claims), “in fluid communication” meansthat fluid can flow from one component to another; such flow may be byway of one or more intermediate (and not specifically mentioned) othercomponents; and such may or may not be selectively interrupted (e.g.,with a valve). As also used herein (including the claims), “coupled”includes two components that are attached (movably or fixedly) by one ormore intermediate components.

1. An apparatus, comprising: a reservoir having a cavity, the cavitycontaining one or more masses of a solid drug, wherein the solid drug issparingly water soluble; an outlet in fluid communication with thecavity; and a vehicle source in fluid communication with the cavity. 2.The apparatus of claim 1, further comprising a tube having a terminalcomponent configured to deliver a combination of vehicle and entraineddrug from the one or more solid drug masses to a target region of ahuman or other animal, wherein the outlet is located on the terminalcomponent.
 3. The apparatus of claim 2, wherein the terminal componentcomprises at least one of a needle, a cochlear implant electrode, acochlear catheter, a bone needle and an open end of a catheter.
 4. Theapparatus of claim 2, wherein the terminal component includes a porousmember configured for introduction of drug into the target region. 5.The apparatus of claim 1, further comprising a three-dimensionalantibacterial filter interposed in a fluid path between the cavity andthe outlet.
 6. The apparatus of claim 5, further comprising a gas reliefport on an upstream side of the antibacterial filter.
 7. The apparatusof claim 1, further comprising a porous element positioned to preventmigration of the one or more solid drug masses from the cavity.
 8. Theapparatus of claim 7, wherein the porous element comprises one or morescreens.
 9. The apparatus of claim 1, further comprising a pumpconfigured to propel vehicle so that said vehicle flows from the cavityto the outlet.
 10. The apparatus of claim 9, wherein the pump isexternal to a housing for the reservoir.
 11. The apparatus of claim 9,wherein the pump and the reservoir are contained within the samehousing.
 12. The apparatus of claim 1, wherein the reservoir isconfigured for non-destructive opening and fluid-tight reclosure so asto permit replenishment of the one or more solid drug masses.
 13. Theapparatus of claim 1, further comprising an electronics package and oneor more electrodes configured to move charged drug entrained in thevehicle.
 14. The apparatus of claim 13, wherein the one or moreelectrodes includes a first electrode in the cavity and a secondelectrode positioned at the outlet, and wherein the electronics packageis configured to charge the first and second electrodes with oppositepolarities.
 15. The apparatus of claim 1, comprising an electronicspackage and one or more electrodes configured to provide electricalstimulation to a tissue in a human or other animal.
 16. The apparatus ofclaim 1, further comprising an electronics package and one or moremagnetic coils configured to produce a magnetic field so as to propelparticles in the vehicle when said vehicle is located in the apparatus.17. The apparatus of claim 16, wherein the particles are magneticnanoparticles.
 18. The apparatus of clam 1, further comprising at leasttwo fluid conduits, each of the fluid conduits having a first opening influid communication with the cavity and a second opening positionableremotely from the cavity, wherein the apparatus is configured to expelvehicle and entrained drug from the one or more solid drug masses fromone of the second openings and to receive fluid through the other ofsaid second openings.
 19. The apparatus of claim 18, wherein the vehicleis a physiological fluid, and wherein the other of the second openingsis configurable to receive the physiological fluid vehicle.
 20. Theapparatus of claim 1, further including a subcutaneously implantableport.
 21. The apparatus of claim 20, wherein the reservoir is part ofthe subcutaneously implantable port.
 22. The apparatus of claim 1,wherein the reservoir includes a semi-permeable membrane or one-wayvalve positioned to admit physiological fluid into the cavity.
 23. Theapparatus of claim 1, further comprising an electronics package and oneor more sensors configured to sense, as to vehicle and entrained drugfrom the one or more solid drug masses, one or more of the following:pH, absorbance of light, electrical conductivity, light scattering, drugconcentration and electrolyte concentration.
 24. The apparatus of claim1, further comprising an electronics package and one or more sensorsconfigured to sense sound.
 25. The apparatus of claim 1, furthercomprising an electronics package and one or more sensors configured tosense tissue electrical activity.
 26. A method, comprising: implanting areservoir into a human or other animal, the reservoir containing a massof a solid form of a drug that is sparingly water-soluble; passingvehicle from a source past the solid drug mass so as to entrain drugfrom the mass; and delivering the passed vehicle and entrained drug to atarget tissue in the human or other animal.
 27. The method of claim 26,further comprising determining a desired therapeutically-effectiveconcentration of the drug, and wherein the solid form of the drug is abasic form and the vehicle includes an acid at a concentration that issubstantially the same as the desired therapeutically-effectiveconcentration.
 28. The method of claim 27, wherein the acid is at leastone of hydrochloric acid, phosphoric acid, monosodium phosphate, citricacid, a sodium salt of citric acid and lactic acid.
 29. The method ofclaim 28, wherein the drug is gacyclidine.
 30. The method of claim 26,wherein the vehicle is at least one of Ringer's solution, lactatedRinger's solution, artificial perilymph and physiological saline. 31.The method of claim 26, further comprising determining a desiredtherapeutically-effective concentration of the drug, and wherein thesolid form of the drug is an acidic form and the vehicle includes a baseat a concentration that is substantially the same as the desiredtherapeutically-effective concentration.
 32. The method of claim 31,wherein the base is at least one of sodium bicarbonate, sodium hydroxideand choline hydroxide.
 33. The method of claim 26, wherein the vehicleincludes a component having an amphipathic molecule.
 34. The method ofclaim 33, wherein the component is one or more of polysorbate 80, anacyl glycerol, a poly-oxyethylene ester of 12-hydroxystearic acid,beta-cyclodextrin, a bile acid such as taurocholic acid,tauroursodeoxycholic acid, cholic acid or ursodeoxycholic acid, anaturally occurring anionic surfactant such as galactocerebrosidesulfate, a naturally occurring neutral surfactant such aslactosylceramide or a naturally occurring zwitterionic surfactant suchas sphingomyelin, phosphatidyl choline or palmitoyl carnitine.
 35. Themethod of claim 26, wherein the vehicle comprises a suspension of atleast one of the following: small particles (100 nm to 0.1 mm in size),or nanoparticles (10 nm to 100 nm in size) having an affinity for thedrug.
 36. The method of claim 35 wherein the small particles ornanoparticles comprise one or more of polylactic acid, polyglycolicacid, a co-polymer of lactic acid and glycolic acid, polypropylene,polyethylene, polystyrene and a magnetic material.
 37. The method ofclaim 26, wherein the vehicle comprises a physiological fluid.
 38. Themethod of claim 37, wherein the vehicle comprises at least one ofcochlear perilymph, cerebrospinal fluid and interstitial fluid.
 39. Amethod for forming pellets of gacyclidine base, comprising: heatingsolid gacyclidine base to form melted gacyclidine base; and cooling themelted gacyclidine base to form pellets of gacyclidine of apredetermined shape.